The present invention relates to an image forming apparatus and particularly to an image forming apparatus using a liquid developing agent.
An image forming apparatus such as an electrophotographic apparatus, an electrostatic recording apparatus, or the like, using a liquid developing agent, has an advantage which cannot be realized by an image forming apparatus using a dry developing agent. Its value has been reconsidered in recent years. That is, main advantages of a wet image forming apparatus are that high image quality can be realized since very fine toner of a sub-micron size can be used, that it is economic since a sufficient image density can be obtained by a small amount of toner, and that an image quality equivalent to printing can be obtained.
Meanwhile, a wet image forming apparatus using conventional liquid toner has several problems. Therefore, the dry technique has been an occupant so long. As one of these problems, a problem in transfer will be mentioned. The first problem in transfer is deterioration of image quality. That is, conventionally, a toner image on a photoconductive member is directly transferred to a paper by a transfer means using an electric field, so that uneven transfer is caused due to fluctuation of the electric field corresponding to convexes and concaves on the paper surface. In addition, transfer errors are easily caused due to fluctuation of electric characteristics and environmental dependency of papers, so that the image quality of transferred images is greatly deteriorated.
To solve these problems, a proposal has been made for an apparatus which once transfers a toner image from a photoconductive member to an intermediate transfer member and thereafter transfers it to a paper. U.S. Pat. Nos. 5,148,222, 5,166,734, and 5,208,637 disclose an apparatus which transfers a toner image from a photoconductive member to an intermediate member by an electric field and thereafter transfers it to a paper by pressure (and heat).
According to these apparatuses, it is relatively easy to form the intermediate transfer member from a material which has a flat surface and less variants and changes in electric resistance. Therefore, compared with the case of directly transferring a toner image on a photoconductive member to a paper, deterioration of image quality due to transfer is improved although a transfer efficiency of 100% cannot be achieved. In addition, since the electric field transfer uses electrophoresis, a large amount of solvent must remain in the toner image at the time of transfer. This solvent moves to the intermediate member and is vaporized by heat, thereby causing a problem that a large amount of vapor of the solvent is generated.
Meanwhile, Japanese Patent Application KOKOKU Publication No. 46-41679, Japanese Patent Application KOKAI Publication No. 62-280882, and the like disclose an apparatus which does not use the electric field transfer but utilizes pressure (and heat) in both of transfer from a photoconductive member to an intermediate transfer member and transfer from the intermediate transfer member to a paper. According to these apparatuses, image quality is less deteriorated. Further, in many cases, the solvent in the toner image is substantially vaporized before the primary transfer from the photoconductive member to the intermediate transfer member, thereby to reduce the solvent in the toner image as much as possible. As a result, generated vapor of solvent is reduced.
However, if pressure (and heat) is thus used in both of the transfer from the photoconductive to the intermediate member and the transfer from the intermediate member to a paper, it is difficult to optimize releasing characteristic (surface energy) of the surfaces of the intermediate member and the photoconductive member, so that excellent transfer is difficult to carry out stably.
As a countermeasure thereof, the intermediate member is formed of an elastic member having relatively low surface energy, and the surface of the intermediate transfer member is provided with an appropriate tack characteristic. In the step of the primary transfer of the toner image from the photoconductive member to the intermediate transfer member, the transfer is carried out using mainly the tack characteristic (slight adhesion) between the intermediate transfer member and toner, and in the step of secondary transfer of the toner image from the intermediate member to a paper, a method in which fixing is simultaneously performed at the same time as the transfer by pressure and heat, using the releasing characteristic has been considered. This method is proposed by the present inventors (Japanese Patent Applications No. 11-235488 and 11-269265).
However, in this method, it is difficult to maintain the tack force of the intermediate member for a long period. In addition, the releasing characteristic of the intermediate member influences the secondary transfer. Particularly, in case where the intermediate transfer member is made of silicone-based material, the silicone oil component having a low molecular weight oozes out to its surface, thereby to improve the releasing characteristic. However, if the intermediate member is exposed to solvent of liquid toner for a long period, the releasing characteristic is spoiled. As a result of this, transfer performance is degraded in both of the primary transfer step and the secondary transfer step.
If material having a tackiness is used for the intermediate member, a paper is strongly adhered to the intermediate member, at the time of fixing simultaneously performed together with transfer. Consequently, the paper is difficult to pass through, with a peeling means such as a peeling claw or the like which is generally used.
An object of the present invention is to provide an image forming apparatus which comprises an intermediate transfer member, has excellent transfer characteristics, and is thereby capable of forming an image with high image quality.
Another object of the present invention is to provide an image forming method which uses an intermediate transfer member, has excellent transfer characteristics, and is thereby capable of forming an image with high image quality.
According to the present invention, there is provided an image forming apparatus comprising: an image carrier; an electrostatic latent image forming mechanism which forms an electrostatic latent image on the image carrier; a developing mechanism which develops the electrostatic latent image on the image carrier to attain a visible image; a first transfer mechanism which presses an intermediate transfer member into contact with the image carrier, to transfer the visible image on the image carrier to the intermediate transfer member; an application mechanism which applies a viscous material onto the intermediate transfer member; and a second transfer mechanism which transfers a transferred image transferred to the intermediate transfer member to a transfer member to which transfer is to be done.
Also, according to the present invention, there is provided an image forming apparatus comprising: an image carrier; an electrostatic latent image forming mechanism which forms an electrostatic latent image on the image carrier; a developing mechanism which develops the electrostatic latent image on the image carrier to attain a visible image; a first transfer mechanism which presses an intermediate transfer member into contact with the image carrier, to transfer the visible image on the image carrier to the intermediate transfer member; an application mechanism which applies a releasing agent onto the intermediate transfer member, in an upstream side of the first transfer mechanism; and a second transfer mechanism which transfers a transferred image transferred to the intermediate transfer member to a transfer member to which transfer is to be done, by applying pressure and heat thereto.
Further, according to the present invention, there is provided an image forming apparatus comprising: an image carrier; an electrostatic latent image forming mechanism which forms an electrostatic latent image on the image carrier; a developing mechanism which develops the electrostatic latent image on the image carrier to attain a visible image; a first transfer mechanism which presses an intermediate transfer member into contact with the image carrier, to transfer the visible image on the image carrier to the intermediate transfer member; a second transfer mechanism which transfers a transferred image transferred to the intermediate transfer member to a transfer member to which transfer is to be done; a first application mechanism which applies a first adhesive agent onto the intermediate transfer member, after the transferred image on the intermediate transfer member is transferred to the transfer member to which transfer is to be done, at the second transfer mechanism, before the visible image on the image carrier is transferred to the intermediate transfer member, at the first transfer mechanism; and a second application mechanism which applies a second adhesive agent onto the intermediate transfer member, after the visible image on the image carrier is transferred to the intermediate transfer member, at the first transfer mechanism, before the transferred image on the intermediate transfer member is transferred to the transfer member to which transfer is to be done, at the first transfer mechanism.
Also further, according to the present invention, there is provided an image forming apparatus comprising: an image carrier; an electrostatic latent image which forms an electrostatic latent image on the image carrier; a developing mechanism which develops the electrostatic latent image on the image carrier to attain a visible image; a first transfer mechanism which presses a belt-like intermediate transfer member into contact with the image carrier, to transfer the visible image on the image carrier to the intermediate transfer member; a second transfer mechanism which presses the belt-like intermediate transfer member into contact with a transfer member to which transfer is to be done, by a transfer roller and a pressure application member opposed thereto, thereby to transfer a transferred image on the belt-like intermediate transfer member to the transfer member to which transfer is to be done; and a separation mechanism which is provided in a downstream side of the second transfer mechanism and has a curvature larger than that of the transfer roller, to separate the transfer member to which transfer is to be done, from the belt-like intermediate transfer member.
Also, according to the present invention, there is provided an image forming apparatus comprising: an image carrier; an electrostatic latent image which forms an electrostatic latent image on the image carrier; a developing mechanism which develops the electrostatic latent image on the image carrier to attain a visible image; a first transfer mechanism which presses a belt-like intermediate transfer member into contact with the image carrier, to transfer the visible image on the image carrier to the intermediate transfer member; a pre-heat roller which is provided in a downstream side of the first transfer mechanism and heats the belt-like intermediate transfer member from a back surface of the belt-like intermediate transfer member; and a second transfer mechanism which presses the belt-like intermediate transfer member into contact with a transfer member to which transfer is to be done, by a pressure application member, thereby to transfer a transferred image on the belt-like intermediate transfer member to the transfer member to which transfer is to be done, and has a curvature larger than a diameter of 30 mm, thereby to separate the transfer member to which transfer is to be done, from the belt-like intermediate transfer member.
Further, according to the present invention, there is provided an image forming apparatus comprising: an image carrier; an electrostatic latent image which forms an electrostatic latent image on the image carrier; a developing mechanism which develops the electrostatic latent image on the image carrier to attain a visible image; a first transfer mechanism which presses a belt-like intermediate transfer member into contact with the image carrier, to transfer the visible image on the image carrier to the intermediate transfer member; a pre-heat tight contact member which is provided in a downstream side of the first transfer mechanism, heats the belt-like intermediate transfer member from a back surface of the belt-like intermediate transfer member, and lets the belt-like intermediate transfer member be into tight contact with the transfer member to which the belt-like intermediate transfer member, by a pressure application member; and a second transfer mechanism which is provided in a downstream side of the first transfer mechanism, presses the belt-like intermediate transfer member into contact with a transfer member to which transfer is to be done, by a pressure application member, thereby to transfer a transferred image on the belt-like intermediate transfer member to the transfer member to which transfer is to be done, and has a curvature larger than a diameter of 30 mm, thereby to separate the transfer member to which transfer is to be done, from the belt-like intermediate transfer member, wherein a pressure applied to the belt-like intermediate transfer member and the transfer member to which transfer is to be done at the pre-heat tight contact mechanism at the second transfer mechanism is larger than a pressure applied to the belt-like intermediate transfer member and the transfer member to which transfer is to be done at the pre-heat tight contact mechanism.
Also further, according to the present invention, there is provided an image forming method comprising: a step of forming an electrostatic latent image on an image carrier; a step of developing the electrostatic latent image on the image carrier to attain a visible image; a first transfer step of pressing an intermediate transfer member into contact with the image carrier, to transfer the visible image on the image carrier to the intermediate transfer member; a step of applying an adhesive agent or releasing agent onto the intermediate transfer member; and a second transfer step of transferring a transferred image transferred to the intermediate transfer member to a transfer member to which transfer is to be done.
Further, according to the present invention, there is provided an image forming method comprising: a step of an electrostatic latent image which forms an electrostatic latent image on an image carrier; a step of developing the electrostatic latent image on the image carrier to attain a visible image; a first transfer step of pressing an intermediate transfer member into contact with the image carrier, to transfer the visible image on the image carrier to the intermediate transfer member; a second transfer step of transferring a transferred image transferred to the intermediate transfer member to a transfer member to which transfer is to be done; a first application step of applying a first adhesive agent onto the intermediate transfer member, after the transferred image on the intermediate transfer member is transferred to the transfer member to which transfer is to be done, at the second transfer step, before the visible image on the image carrier is transferred to the intermediate transfer member, at the first transfer mechanism; and a second application step of applying a second adhesive agent to the intermediate transfer member, after the visible image on the image carrier is transferred to the intermediate transfer member, at the first transfer step, before the transferred image on the intermediate transfer member is transferred to the transfer member to which transfer is to be done, at the first transfer step.
Also further, according to the present invention, there is provided an image forming method comprising: a step of an electrostatic latent image which forms an electrostatic latent image on an image carrier; a step of developing the electrostatic latent image on the image carrier to attain a visible image; a first transfer step of pressing a belt-like intermediate transfer member into contact with the image carrier, to transfer the visible image on the image carrier to the intermediate transfer member; a second transfer step of pressing the belt-like intermediate transfer member into contact with a transfer member to which transfer is to be done, by a transfer roller and a pressure application member opposed thereto, thereby to transfer a transferred image on the belt-like intermediate transfer member to the transfer member to which transfer is to be done; and a step of separating the transfer member to which transfer is to be done, from the belt-like intermediate transfer member, by a separation roller which is provided in a downstream side of the second transfer mechanism and has a curvature larger than that of the transfer roller.